Advanced Multidimensional Modeling of Gasoline-Ethanol Injection in the Flash-Boiling Regime
Today, significant progress is still expected in regards to the greenhouse gas emissions from internal combustion engines and electrified hybrid vehicles. Gasoline direct injection (GDI) engines offer a cheap promising technological approach to achieve these goals, compared to Diesel. But many complex phenomena remain poorly understood and hinder innovation. Among critical processes, liquid fuel injection understanding is a key point for the improvement of internal combustion engines efficiencies. Therefore, there is a clear interest to understand the underlying physics governing the in-nozzle cavitation and flash-boiling of fuels, such as gasoline and biofuels (ethanol,…). Enhanced understanding of such phenomena will enable the development of predictive three dimensional (3D) simulation tools that will give us full use and the involvement of such mechanisms in future engines.
In this thesis, we will continue our on-going work [1-7] on a 3D unified approach to model the injection of any type of injector and fuel, whether diesel or gasoline, and under subcritical and supercritical conditions. This unified approach aims to simulate the full chain from the in-nozzle liquid flow to the combustion, using a unique computational domain, thus allowing more straightforward analysis of the relation between the injection system (nozzle shapes or imperfections, for instance) and the emitted pollutants. This unified approach may also have the nice advantage of avoiding uncertainties on the conventional Eulerian-Lagrangian (EL) injection boundary conditions. Full physical processes chain must be considered in this unified approach, including:
- In-nozzle cavitation and flash-boiling phenomena,
- Classical primary atomization and “flash-atomization”,
- Eulerian-Eulerian (EE) and EL sprays coupling.
Up to now, the above three points have been addressed partly in different projects [1-3]. These works was based on our in-house code IFP-C3D [8]. A real fluid compressible two-phase flow model based on EE approach with the consideration of phase equilibrium has been implemented IFP-C3D. Particularly, a fully compressible balance equation system which includes a 6-equations non-equilibrium model with liquid and gas phase balance equations solved separately; and a 4-equations model which solves the liquid and gas balance equations in mechanical equilibrium and thermal equilibrium. A real fluid equation of state (Peng-Robinson EoS) has been selected to close both systems and to deal with eventual phase change and separation. Currently, a phase equilibrium solver including TP-flash, negative flash, stability test-TPD (Tangent plane distance), UV flash (Isochoric–isoenergetic flash) has been developed and validated [4, 9-11]. A series of test cases involving the evaporation and condensation phenomena performed under subcritical and supercritical conditions have been simulated and compared with available literature data and analytical results. Reasonable results are achieved for all test cases.
Currently, these models are being transferred in a new simulation platform CONVERGE and the proposed PhD project shall use CONVERGE written in C++.
The main objective of this thesis is to develop a new liquid spray atomization model in the “flash-boiling” regime or “flash-atomization” in the framework of the unified approach explained above. This regime intervenes when the fuel is overheated (before injection) significantly beyond its saturation temperature at the combustion chamber ambient pressure. Indeed, the detailed thermodynamic processes of bubbles nucleation, flash-boiling flows and atomization will be basically and numerically studied using fully compressible Eulerian-Eulerian (EE) two-phase models and original thermodynamic methods.
Appropriate real fluid equations of state will be considered along with IFPEN advanced thermodynamic solvers allowing flash-boiling and cavitation for a mixture of gasoline and alcohols like ethanol. More precisely, this thesis is aimed to extend the flash equilibrium solvers (UV) currently developed at IFPEN [4, 9-11] to oxygenated and retrograde fuels. Dealing with such mixture will be the first challenge of this thesis.
The second challenge is related to development of a coupling method between the EE and the EL two-phase formulations of the Converge™ code. Indeed, flash-atomization can produce big droplets with high stokes numbers in case of moderated superheating. These spray droplets are then transported and evaporated in the EL framework [12-14].
Finally, the validation of the developed models will be carried out using available experiments for GDI injectors under flash-boiling conditions, such as the ECN (Engine combustion Network) experimental databases. This work will finally be published in Journals with high impact factors.
Reference
[1] C. Habchi, A Gibbs Energy Relaxation (GERM) Model for Cavitation Simulation. Atomization and Sprays, 2015. 25(4).
[2] C. Habchi, J. Bohbot, A. Schmid, K. Herrmann, A comprehensive Two-Fluid Model for Cavitation and Primary Atomization Modelling of liquid jets – Application to a large marine Diesel injector, J. Phys.: Conf. Ser. 656 (2015) 12084.
[3] B.M. Devassy, C. Habchi, E. Daniel, Atomization Modelling Of Liquid Jets Using A Two-Surface-Density Approach, Atomiz Spr 25 (1) (2015) 47–80
[4] P. Yi, S. Yang, C. Habchi, R. Lugo, A multi-component fully compressible four-equation model with Peng-Robinson equation of state for two-phase flow simulation. (Submitted to Int. J. Multiphase flows, March 2018).
[5] Saurel, R., & Lemetayer, O. (2001) Journal of Fluid Mechanics, 431, 239-271
[6] Saurel, R., Petitpas, F., & Abgrall, R. (2008) Journal of Fluid Mechanics, 607, 313-350
[7] Saurel, R., Boivin, P., & Le Métayer, O. (2016) Computers & Fluids, 128, 53-64
[8] J. Bohbot, N. Gillet, A. Benkenida, IFP-C3D: an unstructured parallel solver for reactive compressible gas flow with spray. Oil & Gas Science and Technology-Revue de l’IFP, 2009. 64(3): p. 309-335.
[9] Le Métayer, O., Massoni, J., & Saurel, R. (2013) Esaim: Proceedings, 40,103-123. EDP Sciences
[10] Chiapolino, A., Boivin, P., & Saurel, R. (2017) Inter. J. for Num. Methods in Fluids, 83(7), 583-605
[11] Chiapolino, A., Boivin, P., & Saurel, R. (2017) Computers & Fluids, 150, 31-45
[12]C. Habchi, The Energy Spectrum Analogy Breakup (Sab) Model For The Numerical Simulation Of Sprays, Atomiz Spr 21 (12) (2011) 1033–1057.
[13]V. Ebrahimian and C. Habchi, Towards a predictive evaporation model for multi-component hydrocarbon droplets at all pressure conditions. Int. J. of Heat and Mass Transfer, 2011. 54(15): p. 3552-3565.
[14] Saurel, R., Chinnayya, A. and Carmouze, Q. (2017) Modelling compressible dense and dilute two-phase flows.
Physics of Fluids,
29(6), 063301
| Academic supervisor |
Prof. Richard SAUREL (AMU) and Dr. Chaouki HABCHI (IFPEN) |
| Doctoral School |
Paris-Saclay University, SMEMaG-ED579 « Fluides, Energétique, Procédés», https://www.universite-paris-saclay.fr/fr/formation/doctorat/sciences-mecaniques-et-energetiques-materiaux-et-geosciences-smemag#l-ecole-doctorale |
| IFPEN supervisors |
Dr. Chaouki HABCHI, IFPEN, Engine & Vehicle Modelling Dept., chaouki.Habchi@ifpen.fr (contact)
Dr. Rafael LUGO, IFPEN, Thermodynamics & Molecular Modeling Dept., rafael.Lugo@ifpen.fr |
| PhD location |
IFPEN, Rueil-Malmaison, France |
| Duration and start date |
3 years, starting preferably on October 1, 2018 |
| Employer |
IFPEN, Rueil-Malmaison, France |
| Academic requirements |
MSc in fluid mechanics, thermodynamics and numerical modelling |
| Language requirements |
Fluency in English, willingness to learn French |
| Other requirements |
Very good proficiencies in numerical simulation and programming (C, C++, FORTRAN90, MPI); first relevant experience in 3D two-phase flow modelling appreciated |
| gross salary |
2500 €/month |
For more information or to submit an application, see
http://theses.ifpen.fr/jcms/r_8284/fr/sujets-de-these-2018 or contact Dr. Chaouki HABCHI (
chaouki.Habchi@ifpen.fr).
About IFP Energies nouvelles
IFP Energies nouvelles is a French public-sector research, innovation and training center. Its mission is to develop efficient, economical, clean and sustainable technologies in the fields of energy, transport and the environment. For more information, see
www.ifpen.fr.
IFPEN offers a stimulating research environment, with access to first in class laboratory infrastructures and computing facilities. IFPEN offers competitive salary and benefits packages. All PhD students have access to dedicated seminars and training sessions.
